Rosenior was quizzed on his team's results and insisted "it is not a tactical thing." The Chelsea boss was also willing to take responsibility for his team's poor run.
"I want to protect my players always. I always will. I take responsibility for that lapse in concentration. But that's what it is. That's happened too many times in my time recently for me not to tell the truth as it is," he added.
"For me, we arrived into the final third a lot. We had an edgy start in terms of cheap giveaways that we gave away, then we managed to gain control of the game and were in their half and we were arriving and creating moments which we don't take. We're not clinical enough. Then out of nowhere, it feels like out of nowhere, they score. It's not the first time that that's happened.
"What happens in football, if you are in a run, a difficult run of games against big teams, your energy levels and your confidence levels can drop if the other team score first. That's what happened. [Jordan] Pickford makes a world-class save at 1-0.
"Then we come out in the second half and have control of the game. Then we make a mistake and they're 2-0 up. It gives them even more energy. It's about flow and momentum. We didn't have that in the game today."